Surface cleaning device and cleaning process for cleaning a planar floor surface

ABSTRACT

Surface cleaning device for cleaning an floor surface comprising an inner space forming casing and a liquid dispenser positioned in the inner space. The liquid dispenser 3 comprises a motor driven rotor shaft which defines an axis of rotation. Rotor arms extend radially away from a rotor shaft. Each rotor arm comprises a blade to thrust a volume of liquid medium away from the inner space in a driving direction towards a casing outlet. The liquid dispenser comprises at least one nozzle for jetting a stream of liquid onto the floor surface. The at least one nozzle has a central axis which is inclined positioned in a forward direction with respect to the driving direction under an angle of inclination with respect to the axis of rotation.

The present invention relates to a surface cleaning device and a cleaning process for cleaning a planar floor surface, in particular a planar surface with an open structure, and more in particular for cleaning a sportsfield.

NL1030974 discloses a surface cleaning device for cleaning a porous surface, like a sports field with artificial turf or an open structure concrete. The surface cleaning device is arranged to carry out a wet cleaning process in which under high pressure a liquid medium is jetted onto the floor surface. A stream of liquid medium is jetted to force contaminations out of the porous surface. The surface cleaning device is connectable to a feed supply for supplying the liquid medium. The cleaning device comprises a casing and a liquid dispenser. The casing forms an inner space with a casing outlet for discharging the liquid medium. A rotor is arranged inside the inner space. The rotor is driven in rotation by a motor which is arranged external from the casing. The rotor comprises two rotor arms. Each rotor arm comprises a nozzle at an extreme end of each rotor arm for jetting a stream of liquid under high pressure. The nozzle is downwardly directed to the porous surface, such that a jet of liquid medium hits under high pressure perpendicularly onto the porous surface.

A drawback of this surface cleaning device is that vulnerable floor surfaces like a sportsfield may get damaged by the high pressure treatment.

U.S. Pat. No. 6,594,855 discloses a similar surface cleaning apparatus for cleaning a runway of an airport. The apparatus contains a housing with a centrally positioned bearing bush for mounting a hollow driving shaft. The housing has a lower part formed by a ring-shaped cover and an upper part formed by a peripheral wall with a removal channel. A distributor head is connected to a lower end of the driving shaft. Two U-bend washing arms are laterally arranged and in fluid communication with the distributor head. The washing arms include an inner fluid delivery channel. A nozzle insert is screwed into a lower bent end of each washing arm. Each washing arm is provided with a ventilation baffle which is bent upwards. The ventilation baffles are provided to thrust a volume of liquid medium with dissolved dirt in an upwards direction via a sucking fan wheel towards the removal channel.

U.S. Pat. No. 6,514,354 discloses a similar cleaning device which is called a power wash and reclamation machine. The machine is supported on four ground engaging caster wheels. The machine has a generally disc-shaped housing with a discharge for discharging recovered material. An engine is mounted to a framework for driving a pick-up member inside the housing. The pick-up member includes a spindle and eight arms which rotates to cause retrieved material to be discharged. Each arm includes a straight rod that is secured to the spindle and extends normal to the longitudinal axis of the spindle

EP0400758 discloses a runway cleaning apparatus for removing rubber residuals from an underlying runway surface without significant damaging said underlying surface. The apparatus comprises a mobile support structure which is mounted on wheels. A feed supply for an intake of water is connectable by a swivel connection through a rotating shaft mounted on bearings and into a jet manifold. A motor is mounted to the support structure for driving the jet manifold in rotation at a relatively high-speed. The jet manifold comprises a plurality of water jets which are directed downwardly against the runway surface. A high pressure water jet is generated having a pressure which is greater than 137880 kPa. Each water jet is moved linearly over the runway with a linear speed which is in excess of 32 km/hour.

A drawback of this apparatus and this method is that these are unsuitable for cleaning more vulnerable surfaces, like a top layer of a sports field.

A drawback of these surface cleaning device is also that vulnerable floor surfaces like a sportsfield may get damaged by the high pressure treatment. Additionally, the cleaning process is ineffective which results in a large water and energy consumptions and a long lasting process time.

The general object of the present invention is to at least partially eliminate the above mentioned drawbacks and/or to provide a usable alternative. More specific, it is an object of the invention to provide a surface cleaning device to improve a cleaning process by shortening a process time, reducing a required supply of liquid volume, and/or reducing a required energy input, and/or reducing a required operational liquid medium pressure.

According to the invention, this object is achieved by a surface cleaning device according to claim 1.

According to the invention, a surface cleaning device for cleaning an floor surface is provided. The surface cleaning device comprises a casing and a liquid dispenser. The casing has a circumferential casing wall and a casing top wall which form an inner space.

The casing is open at a bottom side, The casing has a casing outlet for discharging a volume of liquid medium away from the inner space.

The liquid dispenser is positioned inside the inner space. The liquid dispenser is arranged to dispense a liquid medium onto the floor surface.

The liquid dispenser comprises a rotor. The rotor comprises a rotor shaft. The rotor shaft defines an axis of rotation. The rotor shaft comprises at least one rotor arm which extends radially away from the rotor shaft.

The liquid dispenser comprises a motor for rotationally driving the rotor in a driving direction. The motor is arranged for driving the rotor about the axis of rotation.

The liquid dispenser comprises at least one blade. The at least one blade is connected to the at least one rotor arm. The blade has a blade face to thrust a volume of liquid medium during a rotation of the rotor from the inner space in the driving direction towards the casing outlet.

The liquid dispenser comprises at least one nozzle for jetting a stream of liquid onto the floor surface. The at least one nozzle is downwardly directed to the floor surface. The at least one nozzle is connected to the at least one rotor arm.

According to the invention, the surface cleaning device is improved by effectively orienting the at least one nozzle. The at least one nozzle has a central axis which is inclined positioned in a forward direction with respect to the driving direction. The central axis of the at least one nozzle extends under an acute angle of inclination α with respect to the axis of rotation.

The inclined positioned at least one nozzle provides a scooping operation which contributes to a more effective release of dirt particles from the floor surface. In comparison with a perpendicularly directed nozzle. According to the invention, a jet of liquid is directed under an angle onto a dirt particle, such that the jet of liquid may hit the dirt particle at a lower region close to a joint area in between the dirt particle and the floor surface. As a result, the dirt particle will release more quickly. The at least one forwardly inclined nozzle has proven to be of benefit in cleaning porous floor surfaces like sport fields. Released particles are pushed forwards in the driving direction by the jet of liquid. The particles are moved by the jets in a same direction as the thrusting operation of the blades, such that the jets improve the effectiveness of the blades and improve a discharge of particles. Herewith, the cleaning process can be carried out more effectively, such that a process time of a cleaning process can be shortened, and a required liquid and energy supply can be reduced.

Some floor surfaces like a sports field, in particular a sand infill hockey field, may be relatively vulnerable in getting damaged by a high pressure treatment. Such sports field typically have an artificial soft and porous top layer. Such sports field typically have a top layer out of a synthetic material, e.g. artificial grass. The surface cleaning device is in particular beneficial when used in a cleaning process for cleaning a sports field. Advantageously, this effective way of removing particles according to the invention allows a cleaning operation with mitigated operational pressure levels which provides less direct liquid pressure onto the top layer which may prevent damages to the floor surface. Herewith, a runout of a floor surface may be limited and a lifetime of an floor surface, in particular a sports field may be increased.

In an embodiment of the surface cleaning device according to the invention, the central axis of the at least one nozzle has an angle of inclination α of at least 5°. An inclination of at least 5° already provides a significant improvement of the cleaning process. In particular, the at least one nozzle has an angle of inclination of at least 15° to further improve the cleaning process. Preferably, the at least one nozzle has an angle of inclination of at least 30° to achieve an optimum improvement of the cleaning process. In particular, the angle of inclination α is at most 50° in which an advantageous ratio in between a wiping operation and pressure release operation is obtained. Preferably, the angle of inclination α is at most 35° to obtain a substantial pressure release of the dirt particles.

In an embodiment of the surface cleaning device according to the invention, all nozzles are oriented under the same angle of inclination. Advantageously, all nozzles contribute to an improvement of the cleaning process.

In an embodiment of the surface cleaning device according to the invention, the at least one nozzle is positioned behind the blade. The nozzle jets a stream of liquid from behind the blade and does not protrude outside an outer contour of the blade. The blade and nozzle are both connected to the same rotor arm. Seen in a frontal projection in the driving direction, the at least one nozzle is fully shielded by the blade. The blade keeps the nozzle out of an abrasive stream of the particles, like sand particles from a sportsfield to be cleaned. Advantageously, herewith, an abrasive wear of the nozzle is significantly reduced.

In an embodiment of the surface cleaning device according to the invention, each rotor arm is provided with a blade. The rotor comprises a plurality of rotor arms. Preferably, at least one of the rotor arms is provided with a blade but free of a nozzle. Such a rotor arm is also called a blade arm. A rotor arm comprising a nozzle is also called a nozzle arm. It is an insight of the invention that not all rotor arms need to be equipped with a nozzle. Some rotor arms only serve to improve a discharge capacity of the rotor. Preferably, at most half of an amount of rotor arms is provided with a nozzle. Advantageously, the effectiveness of the cleaning process is improved by improving a thrust capacity of the rotor, and so improving a discharge capacity, while maintaining at the same time a release capacity provided by the nozzles.

In a further embodiment of the surface cleaning device according to the invention, the rotor comprises—seen in the driving direction—a sequence of rotor arms of alternately a rotor arm with a nozzle and a rotor arm without a nozzle. The rotor comprises a plurality of rotor arms which are alternately provided with a nozzle. Seen in the driving direction, a rotor arm having only a blade, a blade arm, follows after a rotor arm which has both a blade and a nozzle, a nozzle arm. A nozzle arm followed by a blade arm. In the configuration of the rotor, a blade arm is positioned in between two neighbouring nozzle arms. Herewith, a beneficial ratio in between a thrust and release capacity is achieved.

In an embodiment of the surface cleaning device according to the invention, the rotor comprises an even amount of the rotor arms. Particularly, the rotor comprises an amount of rotor arm pairs, wherein each rotor arm pair includes rotor arms in a 2-fold rotational symmetry. Herewith, a rotor arm is placed opposite another rotor arm over 180°.

In an embodiment of the surface cleaning device according to the invention, the rotor is configured in rotational symmetry. Preferably, the rotor comprises rotor arms which are rotationally spaced in 8-fold rotational symmetry. Advantageously, the nozzle arms and blade arms are equally distributed along a periphery of the rotor to improve a dynamic behaviour of the rotor.

Preferably, the rotor arms of the rotor arm pair include each a nozzle which is positioned at a same radial distance. Advantageously, the rotor arms of a pair are balanced by the placement of the nozzles which contributes to an improved dynamic behaviour. Preferably, each rotor arm of a rotor arm pair comprises only a single nozzle.

In an embodiment of the surface cleaning device according to the invention, the rotor comprises a first rotor arm including a first nozzle and a second rotor arm including a second nozzle, wherein the second nozzle is positioned at a smaller radial distance from the axis of rotation than the first nozzle. In other words, the rotor comprises a first nozzle arm which includes a first nozzle which is positioned at a first radius, and the rotor comprises a second nozzle arm which includes a second nozzle which is positioned at a second radius, wherein the first radius is larger than the second radius. Preferably, each nozzle arm is provided with only a single nozzle. By positioning the nozzles of the rotor at different radii, during operation, the rotor covers a larger area. Especially, in a linear movement of the surface cleaning device, the rotor having such spatially arranged nozzles has an improved cleaning performance. A process time of the cleaning process can be further shortened.

In a further embodiment of the surface cleaning device according to the invention, the rotor comprises at least a first, second, third and fourth rotor arm including each respectively a first, second, third and fourth nozzle which nozzles are each positioned at a different radial distance. In other words, the rotor further comprises a third nozzle arm which includes a third nozzle which is positioned at a third radius, and the rotor comprises a fourth nozzle arm which includes a fourth nozzle which is positioned at a fourth radius, wherein the first radius is larger than the second radius, the second radius is larger than the third radius, and the third radius is larger than the fourth radius. Advantageously, the rotor provides a further increased coverage of a cleaning area, such that a process time of the cleaning process can be further shortened.

In a preferred embodiment of the surface cleaning device according to the invention, the rotor comprises at least one nozzle arm, wherein each nozzle arm is provided with only a single nozzle. Advantageously, the spatial configuration of the nozzles provides an increase of an area coverage of the rotor which may permit a reduction of necessary nozzles and related savings of a necessary liquid supply. Herewith, the surface cleaning device is especially beneficial in use as a mobile device, e.g. when carried on a front loader of a vehicle.

In an embodiment of the surface cleaning device according to the invention, the blade face of the blade is oriented under an angle of inclination of at least 5°, such that in rotation the blade exerts a lifting thrust on a volume of liquid medium. In particular, the angle of inclination of the blade is at most 50°, in particular at most 30°. Herewith, the blade provides an effective thrust of the volume from the inner space to a casing outlet. Preferably, the casing outlet is positioned tangentially to the circumferential casing wall. A proper ratio in between a lifting and rotationally thrusting capacity is achieved by such an orientation of the blade.

In an embodiment of the surface cleaning device, the cleaning device is installed at a motorised vehicle. In other words, the invention relates to a vehicle, in particular a motorised vehicle comprising a surface cleaning device as described above.

Further, the invention relates to a method, a cleaning process, for cleaning a planar floor surface, in particular a planar porous floor surface, more in particular a planar floor surface with an open structure. The surface cleaning device according to the invention is used in the cleaning process. More in particular, the invention relates to a cleaning process for cleaning a sportsfield. Even more in particular, the invention relates to a cleaning process for cleaning a sportsfield with a fill-in material, e.g. a sand-fill-in material,

The cleaning process according to the invention comprises a step of placing the surface cleaning device onto an floor surface which has to be cleaned; supplying liquid medium from a liquid feed supply; moving the surface cleaning device across the floor surface; operating the liquid dispenser of the surface cleaning device by rotationally driving the rotor in a driving direction; jetting a liquid stream onto the floor surface, wherein the liquid stream is under an angle of inclination with respect to an axis of rotation and forwardly directed with respect to the driving direction.

According to a first aspect, the invention relates to a surface cleaning device for cleaning an floor surface which surface cleaning device comprises a casing and a liquid dispenser, wherein the casing has a circumferential casing wall and a casing top wall which form an inner space, wherein the casing has a casing outlet for discharging a volume of liquid medium away from the inner space, wherein the liquid dispenser is positioned inside the inner space and arranged to dispense a liquid medium onto the floor surface, wherein the liquid dispenser comprises;

-   -   a rotor including a rotor shaft which defines an axis of         rotation and including at least one rotor arm which extends         radially away from the rotor shaft;     -   a motor for rotationally driving the rotor in a driving         direction about the axis of rotation;     -   at least one blade connected to the at least one rotor arm which         blade has a blade face to thrust a volume of liquid medium         during a rotation of the rotor from the inner space in the         driving direction towards the casing outlet;     -   at least one nozzle connected to the at least one rotor arm for         jetting a stream of liquid onto the floor surface, wherein the         at least one nozzle has a central axis which is inclined         positioned in a forward direction with respect to the driving         direction under an angle of inclination α with respect to the         axis of rotation, such that a scooping operation is provided by         the at least one nozzle.

According to a second aspect, the invention relates to a surface cleaning device for cleaning an floor surface which surface cleaning device comprises a casing and a liquid dispenser, wherein the casing has a circumferential casing wall and a casing top wall which form an inner space, wherein the casing has a casing outlet for discharging a volume of liquid medium away from the inner space, wherein the liquid dispenser is positioned inside the inner space and arranged to dispense a liquid medium onto the floor surface, wherein the liquid dispenser comprises:

-   -   a rotor including a rotor shaft which defines an axis of         rotation and including at least one rotor arm which extends         radially away from the rotor shaft;     -   a motor for rotationally driving the rotor in a driving         direction about the axis of rotation;     -   at least one blade connected to the at least one rotor arm which         blade has a blade face to thrust a volume of liquid medium         during a rotation of the rotor from the inner space in the         driving direction towards the casing outlet;     -   at least one nozzle connected to the at least one rotor arm for         jetting a stream of liquid onto the floor surface,

wherein the rotor comprises at least a first and second nozzle arm which each comprises a single nozzle, wherein the first nozzle arm includes a first nozzle which is positioned at a first radius, and wherein the second nozzle arm includes a second nozzle which is positioned at a second radius, wherein the first radius is larger than the second radius.

The invention will be explained in more detail with reference to the appended drawings. The drawings show a practical embodiment according to the invention, which may not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a delimiting feature, not only for the shown embodiment but as a common feature for all embodiments falling within the scope of the appended claims, in which:

FIG. 1 shows in a perspective view a surface cleaning device for cleaning an floor surface;

FIG. 2 shows in a cross sectional top view the cleaning device as shown in FIG. 1;

FIG. 3 shows in a bottom view a rotor with rotor arms of the cleaning device as shown in FIG. 1;

FIG. 4 shows in a schematic view an arrangement of an inclined positioned nozzle behind a blade at a rotor arm of the rotor as shown in FIG. 3;

FIG. 5 shows in a schematic view a cleaning coverage area produced by the rotor as shown in FIG. 3.

Identical reference signs are used in the drawings to indicate identical or functionally similar components. To facilitate comprehension of the description and of the claims the words vertical, horizontal, longitudinal, cross-sectional—with reference to the gravity—are used in a non-limiting way.

FIG. 1 shows a surface cleaning device 1 according to the invention. The cleaning device 1 has a framework 10 which is provided with wheels 11 for supporting the cleaning device 1 to an floor surface. The cleaning device 1 may be a stand-alone device. The cleaning device 1 may be pushed by an operator across the floor surface. Alternatively, the cleaning device 1 may be embodied to be carried by a motorised vehicle. The cleaning device may e.g. be arranged connectable to a front loader of a vehicle.

The cleaning device 1 comprises a housing 12 for housing several machine components. At a lower region, the cleaning device 1 comprises a casing 2. The casing 2 is disc-shaped and is open at a bottom side. The casing 2 has a circumferential casing wall 21 and a casing top wall 22 which form an inner space IS. The casing 2 is arranged for housing a liquid dispenser 3 including a rotor 30 which is positioned inside the inner space IS and further illustrated in FIG. 3.

The liquid dispenser 3 is fluidly connectable to a feed supply for feeding liquid medium to the liquid dispenser. The feed supply may comprise a feed pump and a feed hose to transfer liquid medium to the liquid dispenser 3. The feed supply may be arranged separate from the surface cleaning device, in which the feed hose of the feed supply is connectable to the liquid dispenser of the surface cleaning device. Alternatively, the feed supply may be arranged on-board of the surface cleaning device.

FIG. 2 shows a top view of the surface cleaning device 1, in which the housing 12 is omitted to show driving components of the cleaning device 1.

The casing 2 comprises a casing outlet 23 for discharging a liquid medium away from the inner of the casing 2. The casing outlet 23 is preferably positioned at the circumferential casing wall 21. The casing outlet 23 is oriented in a tangential direction with respect to the circumferential casing wall 21. Alternatively, the casing outlet 23 may be positioned at the casing top wall 22. The casing outlet 23 may be connectable to a filter for separating contaminations from the liquid medium and/or to a reservoir for storing discharged liquid medium.

As shown in FIG. 2, a motor 33 is connected to the framework 10. The motor 33 is arranged for driving the rotor 30 in a driving direction D, as shown in FIG. 3. The rotor 30 is positioned inside the casing 2. The motor 33 is positioned outside the casing 2. The motor 33 may e.g. be an electric motor including batteries or a fuel motor. Typically, the motor 33 provides a power of about 30-40 HP. In an embodiment in which a vehicle is used to carry the surface cleaning device 1, a motor of such vehicle can be used as the motor 33 for driving the rotor 30 of the cleaning device 1. Herewith, a torque provided by the vehicle can be used for driving the rotor 30 of the liquid dispenser 3.

The motor 33 is connected by a belt 37 to a rotor shaft 31 of the rotor. The rotor shaft 31 is arranged vertically and defines an axis of rotation A-A. In normal use, the axis of rotation is directed in a vertical direction. The rotor shaft 31 is centrally positioned at the casing top wall 22. The rotor shaft 31 is journaled by a bearing 39 in a casing top wall 22 of the casing 2. The rotor shaft 31 protrudes through the casing top wall 22. At a top side of the casing 2, a rotor drive wheel 38 is connected to an upper portion of the rotor shaft 31. The rotor drive wheel 38 is in engagement with the belt 37 which is operatively connected to the motor 33.

FIG. 3 shows a bottom view of the cleaning device 1 as shown in FIGS. 1 and 2. The rotor 30 is centrally positioned inside the inner space IS of the casing 2. The inner space is open at a bottom side. The inner space IS is delimited by the circumferential casing wall 21 and the casing top wall 22.

At least one rotor arm 32 is connected to a lower portion of the rotor shaft 31. Here, a rotor distributor 36 is connected to the bottom portion of the rotor shaft 31, which rotor distributor 36 supports the at least one rotor arm 32. The rotor distributor 36 is positioned in the inner space IS of the casing 2. The at least one rotor arm 32 extends radially away from the rotor shaft 31. The rotor shaft 31 and the rotor distributor 36 include at least one fluid channel for supplying a liquid medium to the at least one rotor arm 32.

Preferably, an even amount of rotor arms 32 is connected to the rotor shaft 31. The rotor 30 comprises a plurality of rotor arms 32. Here, the rotor 30 comprises sixteen rotor arms 32.

A blade 34 is connected to the at least one rotor arm 32. Preferably, a blade 34 is connected to each rotor arm 32. The blade 34 comprises a blade face 340 at a front side of the blade 34. The blade face 340 is arranged to thrust during operation a volume of liquid medium from the inner space IS in the driving direction D towards the casing outlet 23. The volume of liquid medium is thrust forwardly. Due to centrifugal forces, the volume of liquid may be thrusted into a tangentially oriented outlet.

Further, at least one rotor arm 32 comprises a nozzle 35. The nozzle is arranged to jet a stream of liquid medium onto an floor surface FS. The nozzle 35 is in fluid communication connected via the rotor shaft 31 to a feed supply of liquid medium. The rotor arm 32 may comprise an internal fluid channel wherein the nozzle is connectable to an outlet of the fluid channel. Alternatively, the nozzle may externally fluidly connected to the rotor arm 32 by a nozzle conduit.

A rotor arm 32 which is provided with a nozzle 35 is here also called a nozzle arm 321. A rotor arm 32 which is not provided with a nozzle, but which rotor arm 320 is provided with a blade 34 is called a blade arm 322.

As shown in FIG. 4, during operation, the nozzle 35 is oriented under an acute angle of inclination α with respect to an axis in parallel with the axis of rotation to provide an inclined stream of liquid medium under a high pressure onto the floor surface FS. The nozzle 35 is directed in a forward direction with respect to the driving direction D. The orientation of the nozzle 35 causes the liquid medium to hit the floor surface FS under an incoming acute angle. In comparison with a perpendicular directed nozzle, the inclined orientation of the nozzle 35 provides an improved release of dirt particles from the floor surface. The incoming angle causes a scooping effect. The inclined nozzle effectively hits the dirt particles which may stick to the floor surface FS at a region close to a sticking area and scoopes the dirt particle away.

Preferably, the incoming angle in between a central axis N-N of the nozzle 35 and the floor surface FS has an angle of inclination α which is at least 5°. This already provides an improved release of dirt particles from a floor surface. More in particular, the angle of inclination α is at least 15° to further improve the release. Preferably, the angle of inclination α is at least 30° to increase a release of dirt particles. A major advantage is that the surface cleaning device can be used for cleaning top surfaces of vulnerable floor surfaces, like sportsfields. Advantageously, the in forward direction inclined nozzle may contribute in saving a water volume necessary for the cleaning operation. Additionally, the inclined nozzle allows an increase of running speed of the surface cleaning device 1 when crossing an floor surface to be cleaned. Herewith, a cleaning process can be carried out more quickly. A higher cleaning quality may be achieved and the cleaning process can be performed in a shorter process time.

In comparison with a perpendicular orientation of a nozzle 35, the acute angle causes a significant portion of the stream of liquid medium to reflect from the floor surface FS in a forward direction with respect to the driving direction D. Particles of dirt which might be captured in orifices of the porousfloor surface are expelled, forced away and released from the floor surface FS. During operation, such a volume V of liquid medium comprising dirt particles will swirl above the floor surface FS in front of a blade face 340. This volume V is then wiped away by the blade 34. The blade face 340 of the blade 34 pushes the volume V away from the inner space IS in the driving direction D towards the casing outlet 23.

Here, the blade 34 is plate-shaped. The blade 34 may be formed from a flat panel. Here, in particular, the blade face 340 is oriented in a same angle of inclination α with respect to the axis of rotation A-A as the nozzle 35. A blade tip 341 is bent forwardly with respect to the blade face 340. Advantageously, the bent provides rigidity to the blade. In particular, the blade face 340 is oriented under an angle of inclination of at least 5°, e.g. 15°, such that the volume V is slightly lifted, but mainly pushed into the direction of the casing outlet 23. Preferably, the blade face is oriented under an angle of at most 50° to obtain a proper ratio in a lifting and thrusting capacity.

As shown in FIG. 4, the nozzle 35 is positioned behind the blade 34. The blade 34 and nozzle 35 are mounted to the same rotor arm 32. Seen in a frontal projection of the driving direction D, the nozzle 35 is fully covered by the blade 34. The nozzle 35 does not protrude outside an outer contour of the blade 34. The nozzle 35 is hided behind the blade 34. Herewith, the blade 34 forms a shield for shielding the nozzle 35 during rotation. An abrasive wear of the nozzle 35 is advantageously strongly reduced by the placement of the nozzle 35 right behind blade 34.

FIG. 3 and corresponding FIG. 5 show a positioning of nozzles 35 at several radii from the axis of rotation A-A. Here, the nozzles are placed at four different radii r1, r2, r3, r4 to increase an area covered by the nozzles during each rotation of the rotor 30. Each nozzle arm supports only a single nozzle 35. The nozzles of several nozzle arms are spaced from each other at a distance of at least 5 cm. In particular, the nozzles are spaced at distance of at least 10 cm. By positioning at least two nozzles 35 at different radii, the area which is covered by the nozzles in each rotation is increased which may further contribute to a shortening of a process time of the cleaning process.

Thus, the invention provides a cleaning process and surface cleaning device 1 for cleaning an floor surface FS comprising an inner space IS forming casing 2 and a liquid dispenser 3 positioned in the inner space IS. The liquid dispenser 3 comprises a motor driven rotor shaft 31 which defines an axis of rotation. Rotor arms 32 extend radially away from a rotor shaft 31. Each rotor arm 32 comprises a blade 34 to thrust a volume V of liquid medium away from the inner space IS in a driving direction D towards a casing outlet 23. The liquid dispenser 3 comprises at least one nozzle for jetting a stream of liquid onto the floor surface FS. The at least one nozzle 35 has a central axis which is inclined positioned in a forward direction with respect to the driving direction D under an angle of inclination α with respect to the axis of rotation A-A.

Although the present invention has been described in detail, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as hereinafter claimed. It is intended that all such changes and modifications be encompassed within the scope of the present disclosure and claims.

List of reference signs: IS inner space FS floor surface LM liquid medium AA axis of rotation NN central axis of nozzle D driving direction α angle of inclination V volume of liquid medium 1 surface cleaning device 2 casing 21 circumferential casing wall 22 casing top wall 23 casing outlet 3 liquid dispenser 30 rotor 31 rotor shaft 32 rotor arm 321 blade arm 322 nozzle arm 33 motor 34 blade 340 blade face 341 blade tip 35 nozzle 35.1; r1 first nozzle/radius 35.2; r2 second nozzle/radius 35.3; r3 third nozzle/radius 35.4; r4 fourth nozzle/radius 36 rotor distributor 37 belt 38 rotor drive wheel 39 bearing 

1. Surface cleaning device for cleaning a floor surface which surface cleaning device comprises: a casing and a liquid dispenser, wherein the casing has a circumferential casing wall and a casing top wall which form an inner space, wherein the casing has a casing outlet for discharging a volume of liquid medium away from the inner space, wherein the liquid dispenser is positioned inside the inner space and arranged to dispense a liquid medium onto the floor surface, and wherein the liquid dispenser comprises: a rotor including a rotor shaft which defines an axis of rotation and including at least one rotor arm which extends radially away from the rotor shaft; a motor for rotationally driving the rotor in a driving direction about the axis of rotation; at least one blade connected to the at least one rotor arm which blade has a blade face to thrust a volume of liquid medium during a rotation of the rotor from the inner space in the driving direction towards the casing outlet; and at least one nozzle connected to the at least one rotor arm for jetting a stream of liquid onto the floor surface, wherein the at least one nozzle has a central axis which is inclined positioned in a forward direction with respect to the driving direction of the rotor under an acute angle of inclination α with respect to the axis of rotation, such that in operation a liquid stream is jetted onto the floor surface, wherein the liquid stream is directed forwardly with respect to the driving direction of the rotor.
 2. Surface cleaning device according to claim 1, wherein the angle of inclination α is at least 5°, in particular at most 50°.
 3. Surface cleaning device according to claim 1, wherein all nozzles are oriented under the same angle of inclination.
 4. Surface cleaning device according to claim 1, wherein the at least one nozzle is positioned behind a blade which blade and nozzle are connected to the same rotor arm, such that the at least one nozzle is—seen in a frontal projection in the driving direction—fully shielded by the blade.
 5. Surface cleaning device according to claim 1, wherein the rotor comprises a plurality of rotor arms, wherein each rotor arm is provided with a blade.
 6. Surface cleaning device according to claim 5, wherein the rotor comprises at least one rotor arm which is provided with a blade and is free of a nozzle, which at least one rotor arm is a so-called blade arm, wherein, in particular, at least half of the amount of rotor arms is a blade arm.
 7. Surface cleaning device according to claim 6, wherein the rotor comprises along its periphery a sequence of rotor arms of alternately a rotor arm with a nozzle, a so-called nozzle arm, and a rotor arm without a nozzle, a so-called blade arm.
 8. Surface cleaning device according to claim 5, wherein the rotor comprises a plurality of rotor arms which are spaced in rotational symmetry, in particular in 8-fold rotational symmetry.
 9. Surface cleaning device according to claim 1, wherein the rotor comprises an amount of rotor arm pairs, wherein each rotor arm of each rotor arm pair includes a nozzle which is positioned at a same radial distance.
 10. Surface cleaning device according to claim 8, wherein the rotor comprises at least a first and second nozzle arm, wherein the first nozzle arm includes a first nozzle which is positioned at a first radius, and wherein the second nozzle arm includes a second nozzle which is positioned at a second radius, wherein the first radius is larger than the second radius.
 11. Surface cleaning device according to claim 10, wherein the rotor further comprises at least a third and in particular a fourth nozzle arm, wherein the third nozzle arm includes a third nozzle which is positioned at a third radius, and wherein in particular the fourth nozzle arm includes a fourth nozzle which is positioned at a fourth radius, wherein the third radius is smaller than the first and second radius, and wherein in particular the fourth radius is smaller than the third radius.
 12. Surface cleaning device according to claim 1, wherein each nozzle arm is provided with a single nozzle.
 13. Surface cleaning device according to claim 1, wherein each blade face is positioned under a blade angle of at most 50° with respect to the axis of rotation, such that in operation the blade exerts a lifting thrust on a volume of liquid medium.
 14. Surface cleaning device according to claim 1, wherein the surface cleaning device is a surface cleaning device configured to clean a planar surface with an open structure, in particular to clean a sportsfield.
 15. Surface cleaning device according to claim 14, wherein the surface cleaning device is a sportsfield cleaning device.
 16. Vehicle, wherein the vehicle comprises a surface cleaning device according to claim
 1. 17. Cleaning process for cleaning a planar floor surface, wherein use made of a surface cleaning device according to claim 1 comprising: placing the surface cleaning device onto the floor surface which has to be cleaned; supplying liquid medium from a liquid feed supply; moving the surface cleaning device across the floor surface; operating the liquid dispenser of the surface cleaning device by rotationally driving the rotor in a driving direction; jetting a liquid stream onto the floor surface, wherein the liquid stream is under an acute angle of inclination with respect to an axis of rotation and directed forwardly with respect to the driving direction of the rotor. 